Datasheet

MAX195
be improved by trimming, but the drift is too great to
provide good stability over temperature. The MAX427
buffer provides the necessary drive current to stabilize
the REF input quickly after capacitance changes.
The reference inaccuracies contribute additional full-
scale error. A reference with less than
1
⁄
2
16
total error
(15 parts per million) over the operating temperature
range is required to limit the additional error to less
than 1LSB. The MAX6241 achieves a drift specification
of 1ppm/°C (typ). This allows reasonable temperature
changes with less than 1LSB error. While the
MAX6241’s initial-accuracy specification (0.02%)
results in an offset error of about ±14LSB, the reference
voltage can be trimmed or the offset can be corrected
in software if absolute DC accuracy is essential. Figure
11’s circuit provides outstanding temperature stability
and also provides excellent DC accuracy if the initial
error is corrected.
16-Bit, 85ksps ADC with 10µA Shutdown
12 ______________________________________________________________________________________
14
16
15
12
MAX195
MAX427
AGNDVSSA
VDDA
4
4
7
6
8
6
2
2
3
MAX874
GND
V
IN
COMP
V
OUT
4.096V
+15V
-15V
47µF
LOW ESR
0.1µF
0.1µF
0.1µF
0.1µF
1000pF
0.1µF
0.1µF
1k
10Ω
2k
REF
1N914
1N914
10Ω
-5V
+5V
6
12
5
4 14
3
2.2µF
V
IN
≥ 8V
1µF
10k
2.2µF
0.1µF
2
MAX6241
IN
OUT
REF
TRIM
NR
GND
AGND
MAX195
Figure 10. Typical Reference Circuit for AC Accuracy
Figure 11. High-Accuracy Reference